Hearing loss common after open heart surgery using CPB, says PGI study

A study conducted by the faculty at Post Graduate Institute of Medical Education and Research (PGIMER) has concluded that open heart surgery using Cardiopulmonary Bypass (CPB) causes significant hearing loss among patients.
CPB is a technique that temporarily takes over functions of the heart and lungs during surgery and maintains circulation of blood and oxygen in the body.
The study on ‘Effects of Cardiopulmonary bypass surgery on auditory functions’ was conducted by PGIMER doctors Dr Sanjay Munjal, Dr Naresh Panda, Dr T Shyam K Singh and Anuradha Sharma and Parul Malik last year and recently won the Dayalan Samuel SSV Award for best paper in Audiology.
A total of 30 patients, aged between 50-70 years, with myocardial infarction (heart attack) scheduled to undergo CPB surgery were referred to PGI’s Speech and Hearing unit from the Advanced Cardiac Centre (ACC). They underwent detailed audiological assessment conducted pre-operatively and two weeks after surgery. The results showed that open heart surgery using CPB led to significant post-operative changes in hearing levels at some frequencies. Further, in some patients, considerable hearing loss was reported immediately after the surgery.
“CPB surgery makes blood redistribution to other organs easy, deviating from the internal ear which is highly susceptible as it lacks collateral circulation and its cells have high energy metabolism. Damage on internal ear micro-circulation causes reduction of cochlear potentials and hence hearing loss,” the study stated.
Apart from this, fluctuation in blood pressure, blood sugar and viral infections also lead to sudden loss of hearing. But CPB surgery is one major surgery after which patients reported hearing loss of varied degrees.
Based on its findings, the study suggested, “Every patient undergoing CPB surgery must be evaluated pre-operatively and post-operatively with the help of audiological battery so that hearing loss, if any, can be detected and managed.”
The study also pointed towards the need for more research to see if this induced dysfunction can be controlled. “We are planning to extend this study on a large sample where the subjects would be followed up for one year to monitor the hearing status and detect delayed onset of hearing loss, if any,” a doctor had mentioned in the study.